The present invention relates to a transistor inverter device in which a circuit is incorporated to control the operation of an inverter when output of this inverter becomes abnormal.
The output of the transistor inverter device varies in accordance with an abnormal state of a load or that of itself. In the case where the operation of an electric discharge lamp is achieved using output of transistor inverter device, for example, discharge is not carried out normally when the end of the life of this electric discharge lamp approaches, and an abnormal state also occurs on an output of the transistor inverter device to which the electric discharge lamp is connected as a load. When this state is left as it is, there is a fear that elements such as transistors, an output transformer and the like constituting the transistor inverter device are damaged. A control circuit for detecting abnormality of the transistor inverter device and stopping the operation of inverter is employed to prevent transistors and the output transformer from being damaged. This control circuit is asked to be constructed as an integrated circuit for the purpose of making the arrangement of device simple and the cost thereof low and attaining high reliability. This circuit integration will be referred to as "IC-ed" in this specification. When the control circuit is formed using the IC, a power source is generally needed to render this IC operative. It is imagined that rectified and smoothed output of transistor inverter circuit is used as this power source. When abnormality is detected and the operation of transistor inverter device is stopped in this case, however, the control circuit comprised of semiconductor integrated circuits is also turned off, thus making it impossible to attain desired control operation. On the other hand, when a different power source is arranged only for use to the control circuit, it undesirably makes the device complicated and the cost thereof high.